Reaction of Trihydridostannyl Complexes with SO2: Preparation of[Re2{Sn2(µ-S)(µ-SO3)2}(CO)4L2{PPh(OEt)2}4] (L ) PPh(OEt)2,

(CH3)3CNC)

Gabriele Albertin,*,† Stefano Antoniutti,† Jesus Castro,‡ and Gianluigi Zanardo†

Dipartimento di Chimica, UniVersita Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy, andDepartamento de Quımica Inorganica, UniVersidade de Vigo, Facultade de Quımica, Edificio de Ciencias

Experimentais, 36310 Vigo (Galicia), Spain

ReceiVed October 22, 2008

Summary: The complexes [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4L2{PPh-(OEt)2}4] (L ) PPh(OEt)2 (1), (CH3)3CNC (2)) were prepared byreaction of the trihydridostannyl compounds Re(SnH3)(CO)2L[PPh-(OEt)2]2 with SO2 under mild conditions. The complexes werecharacterized by spectroscopy and by X-ray crystal structuredetermination of [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{PPh(OEt)2}6] and[Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{(CH3)3CNC}2{PPh(OEt)2}4].

Previous reports1 from our laboratories have dealt with studieson the synthesis and reactivity of the tin trihydride complexes[M]-SnH3 (M ) Mn, Re, Ru, Os) with CO2, which gave newmono- and dinuclear stannyl derivatives. We have now extendedour studies of such SnH3 complexes to their reactivity with SO2

and found a new reaction, giving unprecedented complexescontaining (µ-sulfide)(µ-sulfite)stannyl as a bridging ligand.

Although stannyl complexes of transition metals have beenreported2,3 with a large number of organic and inorganicsubstituents at the tin atom, [M]-SnR3, those containing theSn-S bond are very rare and, to the best of our knowledge,only involve the sulfur-substituted stannyl complexes4

Ru(SnMe2SH)I(CO)(4-CH3C6H4NC)(PPh3)2 and Os{SnMe(1,2-S2C2H4)}(η2-S2CNMe2)(CO)(PPh3)2. No example of eithersulfide-stannyl or sulfite-stannyl complexes has ever beendescribed.

We now report the reaction of the rhenium complexesRe(SnH3)(CO)2L[PPh(OEt)2]2 (L ) PPh(OEt)2, (CH3)3CNC)with SO2, which resulted in the formation of novel thiostannylcomplexes.

Experimental Section

General Comments. All synthetic work was carried out underan appropriate atmosphere (Ar) using standard Schlenk techniques

or in an inert-atmosphere drybox. Once isolated, the complexeswere found to be relatively stable in air but were stored undernitrogen at -25 °C. All solvents were dried over appropriate dryingagents, degassed on a vacuum line, and distilled into vacuum-tightstorage flasks. Re2(CO)10 was a Pressure Chemical Co. product,used as received. The phosphonite PPh(OEt)2 was prepared by themethod of Rabinowitz and Pellon.5 Other reagents were purchasedfrom commercial sources in the highest available purity and usedas received. Infrared spectra were recorded on Nicolet Magna 750or Perkin-Elmer Spectrum-One FT-IR spectrophotometers. NMRspectra (1H, 31P, 13C, 119Sn) were obtained on AC200 and AVANCE300 Bruker spectrometers at temperatures between -90 and +30°C, unless otherwise noted. 1H and 13C spectra are referenced tointernal tetramethylsilane, 31P{1H} chemical shifts are reported withrespect to 85% H3PO4, and 119Sn spectra are referenced with respectto Sn(CH3)4; in all cases downfield shifts are considered positive.COSY, HMQC, and HMBC NMR experiments were performed

* To whom correspondence should be addressed. Fax: +39 041 234 8917.E-mail: albertin@unive.it.

† Universita Ca’ Foscari Venezia.‡ Universidade de Vigo.(1) (a) Albertin, G.; Antoniutti, S.; Bacchi, A.; Bortoluzzi, M.; Pelizzi,

G.; Zanardo, G. Organometallics 2006, 25, 4235–4237. (b) Albertin, G.;Antoniutti, S.; Castro, J.; Garcıa-Fontan, S.; Zanardo, G. Organometallics2007, 26, 2918–2930. (c) Albertin, G.; Antoniutti, S.; Bacchi, A.; Pelizzi,G.; Zanardo, G. Organometallics 2008, 27, 4407–4418.

(2) (a) Mackay, K. M.; Nicholson, B. K. In ComprehensiVe Organo-metallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;Pergamon Press: New York, 1982, Vol. 2, pp 1043-1114. (b) Holt, M. S.;Wilson, W. L.; Nelson, J. H. Chem. ReV. 1989, 89, 11–49. (c) Lappert,M. F.; Rowe, R. S. Coord. Chem. ReV. 1990, 100, 267–292. (d) Davies,A. G. In ComprehensiVe Organometallic Chemistry,; Stone, F. G. A., Abel,E. W., Wilkinson, G., Eds.; Pergamon Press: New York, 1995; Vol. 2, pp218-297. (e) Davies, A. G. Organotin Chemistry; Wiley-VCH: Weinheim,Germany, 2004. (f) Roper, W. R.; Wright, L. J. Organometallics 2006, 25,4704–4718.

(3) (a) Sullivan, R. J.; Brown, T. L. J. Am. Chem. Soc. 1991, 113, 9155–9161. (b) Buil, M. L.; Esteruelas, M. A.; Lahoz, F. J.; Onate, E.; Oro, L. A.J. Am. Chem. Soc. 1995, 117, 3619–3620. (c) Nakazawa, H.; Yamaguchi,Y.; Miyoshi, K. Organometallics 1996, 15, 1337–1339. (d) Schubert, U.;Grubert, S. Organometallics 1996, 15, 4707–4713. (e) Akita, M.; Hua, R.;Nakanishi, S.; Tanaka, M.; Moro-oka, Y. Organometallics 1997, 16, 5572–5584. (f) Utz, T. L.; Leach, P. A.; Geib, S. J.; Cooper, N. J. Chem. Commun.1997, 847–848. (g) Baya, M.; Crochet, P.; Esteruelas, M. A.; Gutierrez-Puebla, E.; Ruiz, N. Organometallics 1999, 18, 5034–5043. (h) Rickard,C. E. F.; Roper, W. R.; Woodman, T. J.; Wright, L. J. Chem. Commun.1999, 837–838. (i) Adams, H.; Broughton, S. G.; Walters, S. J.; Winter,M. J. Chem. Commun. 1999, 1231–1232. (j) Chen, Y.-S.; Ellis, J. E. Inorg.Chim. Acta 2000, 300-302, 675–682. (k) Clark, A. M.; Rickard, C. E. F.;Roper, W. R.; Woodman, T. J.; Wright, L. J. Organometallics 2000, 19,1766–1774. (l) Hermans, S.; Johnson, B. F. G. Chem. Commun. 2000, 1955–1956. (m) Turki, M.; Daniel, C.; Zalis, S.; Vlcek, A., Jr.; van Slageren, J.;Stufkens, D. J. J. Am. Chem. Soc. 2001, 123, 11431–11440. (n) Christendat,D.; Wharf, I.; Lebuis, A.-M.; Butler, I. S.; Gilson, D. F. G. Inorg. Chim.Acta 2002, 329, 36–44. (o) Neale, N. R.; Tilley, T. D. J. Am. Chem. Soc.2002, 124, 3802–3803. (p) Esteruelas, M. A.; Lledos, A.; Maseras, F.;Olivan, M.; Onate, E.; Tajada, M. A.; Tomas, J. Organometallics 2003,22, 2087–2096. (q) Adams, R. D.; Captain, B.; Smith, J. L., Jr.; Hall, M. B.;Beddie, C. L.; Webster, C. E. Inorg. Chem. 2004, 43, 7576–7578. (r) Neale,N. R.; Tilley, T. D. J. Am. Chem. Soc. 2005, 127, 14745–14755. (s) Adams,R. D.; Captain, B.; Herber, R. H.; Johansson, M.; Nowik, I.; Smith, J. L.;Smith, M. D. Inorg. Chem. 2005, 44, 6346–6358. (t) Eguillor, B.; Esteruelas,M. A.; Olivan, M.; Onate, E. Organometallics 2005, 24, 1428–1438. (u)Sagawa, T.; Ohtsuki, K.; Ishiyama, T.; Ozawa, F. Organometallics 2005,24, 1670–1677. (v) Adams, R. D.; Captain, B.; Hollandsworth, C. B.;Johansson, M.; Smith, J. L., Jr. Organometallics 2006, 25, 3848–3855. (w)Alvarez, M. A.; Garcia, M. E.; Ramos, A.; Ruiz, M. A. Organometallics2006, 25, 5374–5380. (x) Braunschweig, H.; Bera, H.; Geibel, B.; Dorfler,R.; Gotz, D.; Seeler, F.; Kupfer, T.; Radacki, K. Eur. J. Inorg. Chem. 2007,3416–3424. (y) Albertin, G.; Antoniutti, S.; Castro, J.; Garcıa-Fontan, S.;Noe, M. Dalton Trans. 2007, 5441–5452. (z) Carlton, L.; Fernandes, M. A.;Sitabule, E. Proc. Natl. Acad. Sci. 2007, 104, 6969–6973.

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(5) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623–4626.

Organometallics 2009, 28, 1270–12731270

10.1021/om801013s CCC: $40.75 2009 American Chemical SocietyPublication on Web 01/16/2009

with standard programs. The SwaN-MR and iNMR softwarepackages6 were used to treat NMR data. The conductivities of 10-3

mol dm-3 solutions of the complexes in CH3NO2 at 25 °C weremeasured on a Radiometer CDM 83 instrument. Elemental analyseswere determined by the Microanalytical Laboratory of the Dipar-timento di Scienze Farmaceutiche, University of Padova, Padova,Italy.

Synthesis of Complexes. The trihydridostannyl complexesRe(SnH3)(CO)2[PPh(OEt)2]3 and Re(SnH3)(CO)2[(CH3)3CNC]-[PPh(OEt)2]2 were prepared by following the reported methods.1b,7

[Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{PPh(OEt)2}6] (1). A solution ofthe trihydridostannyl complex Re(SnH3)(CO)2[PPh(OEt)2]3 (0.2 g,0.21 mmol) in 10 mL of toluene was stirred under a SO2 atmosphere(1 atm) at 0 °C for 30 min. The solvent was removed under reducedpressure to give an oil, which was triturated with ethanol (3 mL).A pale yellow solid slowly separated out, whose precipitation wascompleted by adding hexane (5 mL). The solid was filtered andcrystallized from toluene and hexane; yield g80%.

IR (KBr): νCO 1990, 1928 cm-1 (s). 1H NMR (CD3C6D5, 25 °C):δ 8.05-6.96 (m, 30H, Ph), 4.18, 4.02, 3.80 (m, 24H, CH2), 1.41,1.29, 1.27 (t, 36H, CH3, J ) 7 Hz). 31P{1H} NMR (CD3C6D5, 25°C): AB2 spin system, δA 137.0, δB 132.7, JAB ) 35.5 Hz (J31PA

117Sn

) 317.0, J31PB117Sn ) 276.5 Hz). 13C{1H} NMR (CD3C6D5, 25 °C):

δ 193.2, 192.7 (m, CO), 141-128 (m, Ph), 63.4 (m, CH2), 16.2(m, CH3). 119Sn NMR (CD3C6D5, 25 °C): AB2M spin system, δM

-151.7, JAM ) 329.5, JBM ) 288.0 Hz. Anal. Calcd forC64H90O22P6Re2S3Sn2: C, 36.55; H, 4.31. Found: C, 36.38; H, 4.44.Mp: 147-149 °C dec.

[Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{(CH3)3CNC}2{PPh(OEt)2}4] (2).This complex was prepared exactly like the related complex 1,starting from Re(SnH3)(CO)2[(CH3)3CNC][PPh(OEt)2]2 and usinga reaction time of 40 min; yield g85%.

IR (KBr): νCN 2163 (s); νCO 1976, 1923 cm-1 (s). 1H NMR(CD2Cl2, 25 °C): δ 7.78-7.45 (m, 20H, Ph), 4.08, 3.97, 3.88(m, 16H, CH2), 1.41, 1.35 (t, 24H, CH3 phos, J ) 7 Hz), 1.16(s, 18H, CH3 But). 31P{1H} NMR (CD2Cl2, 25 °C): A2 spinsystem, δ 137.2 (J31P117Sn ) 244.5 Hz). 13C{1H} NMR (CD2Cl2,25 °C): δ 193.9 (t, CO, JCP ) 10.6), 191.1 (t, CO, JCP ) 9.4Hz), 141-128 (m, Ph), 134.9 (br, CN), 63.4 (d, CH2), 58.2 (s,C(CH3)3), 30.1 (s, C(CH3)3), 11.3 (d, CH3 phos). 119Sn NMR(CD2Cl2, 25 °C): A2M spin system, δM -126.8, JAM ) 256.0Hz. Anal. Calcd for C54H78N2O18P4Re2S3Sn2: C, 34.63; H, 4.20;N, 1.50. Found: C, 34.85; H, 4.32; N, 1.41. Mp: 133-135 °Cdec.

Crystal Structure Determination of 1 and 2. Crystallographicdata were collected on a Bruker Smart 1000 CCD diffractometerat CACTI (Universidade de Vigo) using graphite-monochromatedMo KR radiation (λ ) 0.710 73 Å) and were corrected for Lorentzand polarization effects. The software SMART8 was used forcollecting frames of data, indexing reflections, and determininglattice parameters, SAINT9 for integrating the intensity of reflectionsand scaling, and SADABS10 for empirical absorption correction.

The structures were solved and refined with the Oscail program11

by Patterson methods and refined by full-matrix least squares based

on F2.12 For the compound 2, the Squeeze program was used tocorrect the reflection data for the diffuse scattering due to disorderedtoluene solvent.13 Non-hydrogen atoms were refined with aniso-tropic displacement parameters, except, in compound 1, for theatoms labeled as C(1) and C(4), which were refined with isotropicdisplacement parameters. For compound 2 the S-O bond distanceof the terminal oxygen atom O(5) bonded to the sulfur in the sulfitewas fixed to a chemically accepted value. In the case of 1 all ofthe phenyl rings were constrained to be planar. Hydrogen atomswere included in idealized positions and refined with isotropicdisplacement parameters. Crystal data and details of the structuralrefinement are given in Table 1.

Results and Discussion

The trihydridostannyl complexes Re(SnH3)(CO)2L[PPh(OEt)2]2

(L ) PPh(OEt)2, (CH3)3CNC) react with sulfur dioxide under mildconditions (0 °C, 1 atm) to give, as final products, the binuclearcompounds [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4L2{PPh(OEt)2}4] (1, 2)containing both sulfide (µ-S)2- and sulfite (µ-SO3)2- bridgingstannyl ligands (Scheme ).

The reaction proceeds with reduction of SO2 to sulfide, S2-,through a complicated mechanism which probably involves thehydrides of the SnH3 ligand as the reducing agent. Two sulfiteanions, SO3

2-, are also formed in the reaction and, together withS2-, act as bridging groups between the tin atoms.

The progress of the reaction between the [Re]-SnH3 com-plexes and SO2 in CD3C6D5 was monitored by NMR spectros-copy, but no clear information on either the stoichiometry ofthe reaction or the nature of the intermediates was obtained.The reaction was very fast, even at low temperature (-20 °C),and the 1H NMR spectra did not show any new signals exceptfor those of the starting and final complexes 1 and 2. This alsoseems to exclude the formation of free H2,

14 whose presenceshould be shown by a slightly broad signal at ca. 4.6 ppm.15

The 31P NMR spectra of the reaction mixture showed that thesignal of the [Re]-SnH3 precursors disappeared with theconcurrent appearance of the resonance of dinuclear complex1 or 2. Some signals of low intensity, probably intermediates,were also observed, but they disappeared at the end of thereaction and did not give any information on its path.

The reduction of SO2 to sulfide (S2-) by tin hydrides involves6e for each sulfur atom and is really a complicated reaction,which probably proceeds through a series of steps. However,whatever the mechanism may be, the reaction gave theunprecedented dinuclear complexes 1 and 2, containing (µ-sulfide)(µ-sulfite)stannyl as ligand, which were very stable andwere isolated as pale yellow solids and fully characterized. Itwas also noted that substituting one PPh(OEt)2 with tert-butylisocyanide in Re(SnH3)(CO)2[PPh(OEt)2]3 did not change thereaction with SO2, giving the same dinuclear bis(stannyl)complex 2, stabilized by the isocyanide ligand.

Although analytical and spectroscopic data (IR and 1H, 31P,13C, and 119Sn NMR) matched the proposed formulations of thecomplexes, their geometry was deduced by X-ray crystalstructure determinations of [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{PPh-

(6) Balacco, G. J. Chem. Inf. Comput. Sci. 1994, 34, 1235–1241. (http://www.inmr.net/).

(7) Albertin, G.; Antoniutti, S.; Castro, J.; Zanardo, G. Manuscript inpreparation.

(8) SMART Version 5.054, Instrument Control and Data CollectionSoftware; Bruker Analytical X-ray Systems Inc., Madison, WI, 1997.

(9) SAINT Version 6.01, Data Integration Software Package; BrukerAnalytical X-ray Systems Inc., Madison, WI, 1997.

(10) Sheldrick, G. M. SADABS, An Empirical Absorption CorrectionProgram for Area Detector Data; University of Gottingen, Gottingen,Germany, 1996.

(11) McArdle, P. J. Appl. Crystallogr. 1995, 28, 65–65.

(12) Sheldrick, G. M. SHELX-97, Program for the Solution andRefinement of Crystal Structures; University of Gottingen, Gottingen,Germany, 1997.

(13) Spek, A. L. Acta Crystallogr. 1990, A46, C34.(14) The absence of H2 seems to exclude the simple stoichiometry:

2[Re]-SnH3 + 3SO2 f [Re]2-Sn2(µ-S)(µ-SO3)2 + 3H2. Other speciescontaining hydrogen and/or sulfur, which were not identified, probably alsoformed in the reaction.

(15) Crabtree, R. H.; Lavin, M.; Bonneviot, L. J. Am. Chem. Soc. 1986,108, 4032–4037.

Notes Organometallics, Vol. 28, No. 4, 2009 1271

(OEt)2}6] (1) and [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{(CH3)3CNC}2-{PPh(OEt)2}4] (2), whose ORTEP drawings are shown inFigures 1 and S1 (Supporting Information), respectively.Selected bond distances and angles for 1 and 2 are given inTable 2.

Compounds 1 and 2 consist of dimeric units of two rheniumatoms connected by the novel bridging ditin ligand (µ-sulfide)bis(µ-sulfite-κO,O′)ditin. This moiety consists of two tinatoms connected by two SO3

2- (sulfite ions) and a S2- (sulfideion), forming a structure which may be defined as a bicyclo[3.3.1]-nonane where both bridgeheads are tin atoms. In both cases,the oxygen atoms of the sulfite ions out of the bicycle aredirected toward the sulfide atoms, like the wings of the bicycle,leaving the nonbonding electronic pairs almost parallel, as thelegs of the bicycle (see Figure S2 in the Supporting Information).However, this assessment should be made with care, since thepositions of the oxygen atoms are not well established (at leastfor 2; see the Experimental Section). The tin atoms are the donoratoms of this bridging ligand and coordinate to two rheniumatoms. In the case of 1, the coordination sphere of the rheniumatoms is completed by two cis carbonyl ligands and three merdiethoxyphenylphosphonite ligands. In complex 2, one diethox-yphenylphosphonite ligand was substituted by a tert-butylisocyanide molecule, in such a way that the remaining phos-phonite ligands were mutually trans and the tert-butyl isocyanideligand was trans to a carbonyl ligand. Both molecules have asymmetry axis, which is crystallographic (symmetry operation1 - x, y, 0.5 - z) in the case of 2 and makes the two rheniumatoms quite similar in their geometrical parameters. However,the spatial disposition of the ligands is different in both cases.In 2, they are related by the symmetry operation (1 - x, y, 0.5- z) and the consequence is an isocyanide-Re-Re-isocyanideor carbonyl-Re-Re-carbonyl torsion angle close to 90°(average 91.8(3)°) (see Figure S3 in the Supporting Information),but for 1 the corresponding torsion angles are close to 180°(average 160.3(9)°) (see Figure S3).

Table 1. Crystal Data and Structure Refinement Details for 1 and 2

1 2

empirical formula C64H90O22P6Re2S3Sn2 C54H78N2O18P4Re2S3Sn2

formula wt 2103.14 1873.02temp, K 293(2) 293(2)wavelength, Å 0.710 73 0.710 73crystal syst monoclinic monoclinicspace group P21/c C2/cunit cell dimens

a, Å 12.0145(14) 15.347(7)b, Å 29.314(3) 16.615(7)c, Å 25.998(3) 31.222(14)�, deg 115.140(5) 93.489(9)

V, Å3 8289.0(16) 7946(6)Z 4 4calcd density, Mg/m3 1.685 1.566abs coeff, mm-1 3.763 3.873F(000) 4152 3672cryst size. mm 0.25 × 0.08 × 0.07 0.45 × 0.25 × 0.13θ range for

data collecn, deg1.39-20.82 1.81-27.90

index ranges -11 e h e 12; -29 e k e 29;-21 e l e 25

-19 e h e 19; -12 e k e 21;-41 e l e 40

no. of rflns collected 29 497 25 074no. of indep rflns 8654 (R(int) ) 0.1240) 9289 (R(int) ) 0.0441)no. of obsd rflns (>2σ) 4999 5643data completeness 0.999 0.978abs cor semiempirical from equivalentsmax, min transmission 1.000, 0.768 1.000, 0.695refinement method full-matrix least squares on F2

no. of data/restraints/params

8654/0/798 9289/1/391

goodness of fit on F2 0.968 0.928final R indices (I > 2σ(I)) R1 ) 0.0670,

wR2 ) 0.1552R1 ) 0.0394,

wR2 ) 0.0920R indices (all data) R1 ) 0.1282,

wR2 ) 0.1944R1 ) 0.0753,

wR2 ) 0.1032largest diff peak,

hole, e Å-31.692, -0.945 0.849, -0.983

Scheme 1a

a [Re] ) Re(CO)2[PPh(OEt)2]3 (1), Re(CO)2[(CH3)3CNC][PPh-(OEt)2]2 (2).

Figure 1. View of compound 1 drawn at the 30% probability level.The phenyl rings and the ethoxy groups are not shown.

1272 Organometallics, Vol. 28, No. 4, 2009 Notes

In conclusion, the substitution of a phosphonite ligand by aisocyanide ligand causes important spatial changes in themolecule. It is important to note that the tin atoms are out ofthe Re-Re axis, since the different sulfur bridges in the ditinligand cause a large bending of this axis, up to Re-Sn-Sn-Retorsion angles of 7.2(8)° for 1 and 30.2(2)° for 2. This effect ismore evident when the dihedral angles formed by the equatorialcoordination planes are calculated, and they are 23.8(5)° for 1and 30.68(9)° for 2.

The environment of the rhenium atoms in both complexesmay be described as that of a slightly distorted octahedron. Bondlengths around rhenium atoms have values similar to those found

in the literature.1b,7,16-22 In 1, the rhenium atom labeled as Re(2)is slightly distorted with respect to Re(1), due to the steric effecton one of the phosphonites of the bridging sulfite.

The substitution of a phosphonite ligand by a isocyanideligand causes more differences in the compounds. In 2, themutually trans phosphonite ligands are almost perfectly stag-gered, with an average C-P-P-C or O-P-P-O torsion angleof 176.4(3)°. However, for 1, the mutually trans phosphoniteligands are almost perfectly eclipsed, with average C-P-P-Cor O-P-P-O torsion angles of 18.9(9)° for Re(1) and 4.0(9)°for Re(2). In addition, neither rhenium atom has the same spatialarrangement. For that labeled Re(1), the phenyl group is almostperpendicular to the carbonyl trans to the tin atoms (averagetorsion angle C-P-Re(1)-C(2) of 79.5(1)°) whereas anaverage torsion angle C-P-Re(2)-C(3) of 6.7(1)° shows analmost parallel arrangement of the phenyl group in Re(2).

The phosphonite ligand trans to a carbonyl group in 1 has aP-O bond almost parallel to the Re-Sn vector, with torsionangles of 164.6(6)° (Re(1)-Sn(1)-P(1)-O(11)) and 172.9(6)°(Re(2)-Sn(2)-P(5)-O(51)).

The IR and NMR data of both thiostannyl complexes 1 and2 indicate that a geometry of type I (Scheme ), like that observedin the solid state, also occurs in solution.

The IR spectra of both compounds 1 and 2 show two νCO

bands, fitting the mutually cis position of the two carbonylligands. In the spectrum of 2, a strong band at 2163 cm-1,attributed to the νCN of the isocyanide, is also present. The 13CNMR spectra of both compounds indicate the magnetic in-equivalence of the two CO groups, showing two well-separatedmultiplets for the carbonyl carbon resonances at 193.2-193.9and 192.7-191.1 ppm. At temperatures between +30 and -80°C, the 31P NMR spectra of 1 is an AB2 multiplet, indicatingthat two phosphonites are magnetically equivalent and differentfrom the third. Instead, the 31P spectra of complex 2 is a sharpsinglet, fitting the magnetic equivalence of the two phosphoniteligands. 119Sn spectra appear either as a complicated multipletat -151.7 ppm (1) or as a triplet at -126.8 ppm (2), due to thecoupling with the phosphorus nuclei of the phosphonites.Simulations with either an AB2M (1) or an A2M (2) model (M) 119Sn) gave an excellent fit between experimental andcalculated spectra (see Figures S4 and S5 in the SupportingInformation).

On the basis of these data, a geometry of type I may beproposed in solution for dinuclear complexes 1 and 2.

Acknowledgment. Mrs. Daniela Baldan is gratefullyacknowledged for technical assistance.

Supporting Information Available: CIF files and FiguresS1-S3, giving crystallographic data for compounds 1 and 2, andFigures S4 and S5, giving 119Sn{1H} NMR data. This material isavailable free of charge via the Internet at http://pubs.acs.org.

OM801013S

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(22) Huynh, L.; Wang, Z.; Yang, J.; Stoeva, V.; Lough, A.; Manners,I.; Winnik, M. A. Chem. Mater. 2005, 17, 4765–4773.

Table 2. Selected Bond Lengths (Å) and Angles (deg)

Compound 1Re(1)-C(1) 1.86(2) Re(2)-C(4) 1.92(2)Re(1)-C(2) 1.81(2) Re(2)-C(3) 1.88(2)Re(1)-P(1) 2.381(6) Re(2)-P(4) 2.375(6)Re(1)-P(3) 2.372(6) Re(2)-P(6) 2.381(6)Re(1)-P(2) 2.416(6) Re(2)-P(5) 2.411(6)Re(1)-Sn(1) 2.7285(17) Re(2)-Sn(2) 2.7316(16)C(1)-O(1) 1.22(2) C(3)-O(3) 1.14(2)C(2)-O(2) 1.21(2) C(4)-O(4) 1.15(2)Sn(1)-O(1S) 2.084(15) Sn(2)-O(2S) 2.051(15)Sn(1)-O(3S) 2.055(15) Sn(2)-O(4S) 2.041(16)Sn(1)-S(3) 2.400(6) Sn(2)-S(3) 2.415(6)S(1)-O(3S) 1.569(15) S(2)-O(1S) 1.537(17)S(1)-O(4S) 1.573(16) S(2)-O(2S) 1.533(15)S(1)-O(5S) 1.458(18) S(2)-O(6S) 1.45(2)

C(1)-Re(1)-C(2) 90.1(9) C(3)-Re(2)-C(4) 92.2(9)C(2)-Re(1)-P(1) 89.1(6) C(4)-Re(2)-P(4) 88.2(7)C(1)-Re(1)-P(3) 85.8(6) C(4)-Re(2)-P(6) 84.2(7)C(1)-Re(1)-P(1) 88.5(6) C(3)-Re(2)-P(5) 83.4(7)C(2)-Re(1)-P(2) 93.9(7) C(3)-Re(2)-P(6) 89.9(6)P(2)-Re(1)-P(3) 94.7(2) P(5)-Re(2)-P(6) 96.6(2)C(1)-Re(1)-Sn(1) 85.0(6) C(4)-Re(2)-Sn(2) 87.9(6)P(1)-Re(1)-Sn(1) 86.03(14) P(6)-Re(2)-Sn(2) 90.11(15)P(2)-Re(1)-Sn(1) 90.99(15) P(4)-Re(2)-Sn(2) 91.12(14)P(3)-Re(1)-Sn(1) 95.18(15) P(5)-Re(2)-Sn(2) 96.51(13)C(2)-Re(1)-P(3) 89.2(6) C(3)-Re(2)-P(4) 88.9(6)P(1)-Re(1)-P(2) 91.1(2) P(4)-Re(2)-P(5) 90.8(2)C(2)-Re(1)-Sn(1) 173.1(7) C(3)-Re(2)-Sn(2) 179.9(6)P(3)-Re(1)-P(1) 174.0(2) P(4)-Re(2)-P(6) 172.3(2)C(1)-Re(1)-P(2) 176.0(6) C(4)-Re(2)-P(5) 175.5(7)O(1)-C(1)-Re(1) 175.0(17) O(3)-C(3)-Re(2) 177(2)O(2)-C(2)-Re(1) 178.7(18) O(4)-C(4)-Re(2) 175(2)O(3S)-Sn(1)-O(1S) 89.8(7) O(4S)-Sn(2)-O(2S) 90.9(7)O(1S)-Sn(1)-S(3) 103.0(4) O(2S)-Sn(2)-S(3) 101.2(5)O(3S)-Sn(1)-S(3) 102.7(4) O(4S)-Sn(2)-S(3) 100.8(4)O(1S)--Sn(1)-Re(1) 113.9(4) O(2S)-Sn(2)-Re(2) 113.3(5)O(3S)-Sn(1)-Re(1) 106.8(4) O(4S)-Sn(2)-Re(2) 119.2(4)S(3)-Sn(1)-Re(1) 132.01(15) S(3)-Sn(2)-Re(2) 125.06(14)

Compound 2Re-C(1) 1.948(7) Sn-S(1) 2.4165(17)Re-C(2) 1.944(6) Sn-O(3) 2.060(5)Re-P(1) 2.3881(17) Sn-O(4) 2.067(5)Re-P(2) 2.3856(17) S(2)-O(4i) 1.470(5)Re-C(31) 2.065(6) S(2)-O(5) 1.274(14)Re-Sn 2.7383(12) S(2)-O(3) 1.503(5)C(1)-O(1) 1.152(7) N(31)-C(32) 1.489(8)C(2)-O(2) 1.141(7) C(31)-N(31) 1.152(7)

C(1)-Re-C(2) 91.8(3) P(1)-Re-P(2) 177.02(5)C(2)-Re-C(31) 92.7(2) C(1)-Re-C(31) 175.6(2)C(1)-Re-P(1) 89.7(2) O(2)-C(2)-Re 179.3(7)C(1)-Re-P(2) 89.5(2) O(1)-C(1)-Re 178.6(7)C(2)-Re-P(1) 87.2(2) O(3)-Sn-O(4) 93.7(3)C(31)-Re-P(1) 90.93(17) O(3)-Sn-S(1) 103.35(15)C(1)-Re-Sn 92.91(18) O(4)-Sn-S(1) 97.89(15)P(1)-Re-Sn 94.32(4) O(3)-Sn-Re 113.11(14)P(2)-Re-Sn 88.61(4) O(4)-Sn-Re 113.40(14)C(31)-Re-Sn 82.65(16) S(1)-Sn-Re 129.04(5)C(31)-Re-P(2) 90.01(17) C(31)-N(31)-C(32) 172.2(6)C(2)-Re-P(2) 89.9(2) N(31)-C(31)-Re 178.2(5)C(2)-Re-Sn 175.1(2)

Notes Organometallics, Vol. 28, No. 4, 2009 1273